Hydrothermal Synthesis, Crystal Structures and Characterization of Two Hydrogen Phosphates Templated by 4-Amino-2,2,6,6-tetramethylpiperidine

Abstract

Chemical preparations, crystal structures, thermal analyses, and IR spectroscopic studies are given for two new hydrogen phosphates templated by 4-amino-2,2,6,6-tetramethylpiperidine: (C₉H₂₂N₂)₂·(H₂PO₄)·(HPO₄)·(F)·H₂O (I) and (C₉H₂₂N₂)·(H₂PO₄)₂(II). The structures are determined by single crystal X-ray diffraction. Both compounds crystallize in the P2₁/c (N°14) monoclinic space group with the unit cell parameters: a = 14.856 (1) Å, b = 14.092 (2) Å, c = 14.7166 (9) Å, β = 118.434 (7)°, V = 2709.2 (4) Å ³, and Z = 4 for (I) and a = 9.803 (2) Å, c = 0.466 (2) Å, c = 15.640 (8) Å, β = 94.990 (4), V = 1598.68 (7) ų, and Z = 4 for (II).

The structure of I, refined to R = 0.042 and R_w = 0.067 for 6009 reflections (I ≥ 2σ (I)), exhibits infinite inorganic chains _∞((H₂PO₄)·(HPO₄)·(F)·H₂O)⁴⁻ linked together through weak hydrogen bonds to form layers onto which the diprotonated [C₉H₂₂N₂]^{2 +} amine molecules are anchored.

The structure of II, refined to R = 0.060 and R_w = 0.086 for 1435 reflections (I ≥ 2σ (I)), consists of _∞(H₂PO₄)⁻ (100) layers between which [C₉H₂₂N₂]²⁺ cations are inserted. A network of hydrogen bonds connects the different components. IR spectra of I and II show the characteristic bands of amine groups and phosphate anions.

Keywords:

• Crystal structures
• hydrothermal synthesis
• infrared spectroscopy
• organic phosphates
• thermal behavior